Retinas of normal rhesus monkeys were exposed to ruby and argon laser beams using doses identical to those of the clinical treatment of diabetic retinopathy. Also, a small amount of blood was injected into the vitreous to simulate intra-vitreous neovascularization. Argon laser treatment was applied on the thin blood streaks over the retina. Neither laser directly produced obliteration of capillaries. However, after the cellular damage in each lesion was repaired, delayed degeneration of capillaries at the burned areas was observed. Severe damage in the ganglion cells was demonstrated when argon laser was aimed at the thick blood films in the vitreous.